One aspect of this invention relates to the chemotherapeutic control of plant diseases caused by a group of organisms termed mycoplasma-like organisms (MLO) and rickettsia-like organisms (RLO) with a novel chemotherapeutic agent designated KT-198. KT-198 is a tannate complex of picro ammonium formate combined with a minor amount of a surfactant sufficient to prevent formation of ammonium picrates. Both MLO and RLO were previously thought to be viruses since they pass through filters that hold back bacteria and could not be detected by ordinary light microscope. With the development of electron microscopy and new microbiological techniques, these have been shown to be organisms which could be cultivated on special nutrient media, and at least for some of them Koch's postulates have been established. The RLO are walled organisms and inhabit xylem or phloem cells depending on the species concerned. Some of the serious diseases of plants such as phony peach, Pierce's diseases of grapes, citrus greening and die-back, grassy shoot of sugar cane, etc. are examples of RLO diseases.
More than 50 diseases of plants at one time considered to be of viral origin have now been shown to be mycoplasmas (including the motile Spiroplasma). Very important plant diseases such as elm phloem necrosis, yellow lethal wilt of coconut, sandal spike disease, X-disease of peach, pear decline, potato witches broom, corn stunt, yellow dwarf of rice, aster yellows, mulberry dwarf, etc. have been shown to be of MLO origin. More and more examples are being found. Another group of diseases for which the chemotherapeutant of the present invention, KT-198, has been developed is against some of the legume viruses which are seed-borne.
Another aspect of this invention relates to the chemotherapeutic control of plant diseases where the causal organisms are plant pathogenic fungi and bacteria with another novel chemotherapeutic agent of this invention designated KT-19827. KT-19827 is a tannate complex of picro cupric ammonium formate in aqueous solution combined with a minor amount of a surfactant sufficient to prevent formation of ammonium picrate.
This new chemotherapeutic agent is useful in the control of the following types of diseases and similar plant diseases:
(1) Internally and externally seed-borne fungal and bacterial diseases of plants.
(2) Downy mildew and powdery mildews of plants caused by fungi.
(3) Root rots and wilt diseases of plants where the organisms are soil-borne, and where many of the conventional fungicides cannot be used since they affect the living root system.
(4) Systemically infected trees where the fungus is in the vascular tissues and only those systemic fungicides which when injected are translocated inside the vascular strands can be used. As examples, the oak wilt disease and the Dutch elm disease, both caused by different species of the fungus Ceratocystis. These diseases have remained "incurable" up to the present time. The present novel fungicide is the first of its kind which has proved effective in more than 900 treated trees, effectively controlling the disease.
(5) A large number of plant bacterial diseases incited by species of the genus Xanthomonas, Pseudomonas, Erwinia and Corynebacterium, which up to the present were controlled chiefly by the use of antibiotics such as streptomycin and tetracyclines or their combination. Due to the development of antibiotic resistant bacterial strains, such diseases have no direct control measures now. No really effective bactericide is yet available though partial effect has been claimed with many compounds. The novel bactericide of this invention offers the first effective control of phytopathogenic bacterial pathogens, both as seed treatment, plant dips and spray schedules.